The present invention relates to a speaker for generating sounds by vibrating a vibration plate by an electromagnet, and more particularly to an electrodynamic speaker mounted on a printed circuit board of an electronic instrument such as a portable telephone.
In recent years, there is a tendency to mount small electric parts on a printed circuit board, electrodynamic speaker for the small electronic instrument is accordingly mounted on the printed circuit board. Such a printed circuit for the portable telephone is used as a signaling device.
Referring to FIGS. 5 and 6, which are a plan view of a conventional electrodynamic speaker and a sectional view taken along a line VIxe2x80x94VI of FIG. 5 respectively, electrodynamic speaker 50 has a circular frame 51 having a central circular hole 51b and a cubic portion 51a. An annular shoulder 51c is formed on the frame 51 and a pair of cylindrical holes 51d are formed in the cubic portion 51a. A plurality of perforations 51e are formed in the frame 51.
A yoke 52 made of magnetic material and having a dish-shape is secured to the wall of the central hole 51b. A disk-shape magnet 53 is secured on the yoke 52 and a disk-shape top plate 54 is securely mounted on the magnet 53. Thus, a magnetic circuit is formed between the yoke 52 and the top plate 54, interposing the magnet 53.
An annular vibrating plate 55 made of plastic has a spherical central portion, a circular recess 55a at the periphery of the central portion and a peripheral portion 55b. An annular voice coil 56 is fixed to the underside of the recess 55b and inserted in the gap between the periphery of the top plate 54 and an upper portion of the yoke 52.
A pair of lead plates 57, each of which is made of an elongated metal plate, are embedded in the frame 51. Each of the lead plates 57 is extended between a side wall of the cubic portion 51a and an end 57a exposed in the underside of the frame 51. A coil spring 58 is inserted in each hole 51d. An upper end 58a (FIG. 7a) of the coil spring 58 is inserted in a hole 57c formed in an end portion 57b of the lead plate 57 and electrically connected to the lead plate 57 by solder 65 (FIG. 7b). The lower end of the spring 58 is projected from the underside of the frame 51.
Both ends of the coil 56 are soldered to ends 57a of lead plates 57. Thus, the coil 56 is connected to the coil springs 58.
A cover 59 has sound emanating holes 59a and is adhered to the shoulder 51c. 
Here, it is necessary to accurately assemble the coil spring 58 in the hole 51d so as not to contact with the inner wall of the hole 51d. FIGS. 7a and 7b are sectional views showing a method for assembling the coil spring. A positioning jig 90 is provided for positioning the frame 51. The positioning jig 90 has a pair of positioning holes, each comprising a spring positioning hole 90a. 
In the assembling of the coil spring 58, the frame 51 is mounted on the jig 90 as shown in FIG. 7a. The coil spring 58 is inserted in the spring positioning hole 90a of the jig 90 and the hole 51d of the frame 51. The upper end 58a of the coil spring 58 is inserted in the hole 57c of the end portion 57b of the lead plate 57 and the coil spring is compressed by a pressing jig 91. The upper end 58a of the coil spring 58 is connected to the end portion 57b by the solder 65 as shown in FIG. 7b. 
Referring to FIG. 8, the frame 50 is mounted on a printed circuit board 81. The end of the coil spring 58 is pressed against a terminal on the circuit board 81 so that the electric current is applied to the coil 56 to vibrate the vibrating plate 55. The generated sound is emanated from the sound emanating hole 59a. 
FIG. 9 is a sectional view showing a connecting portion of another conventional buzzer. A U-shaped connecting spring plate 62 is connected to a lead plate 61 secured to a case 60 of the speaker by solder 63 at an end thereof. Another end of the spring plate 62 is pressed against a terminal of a printed circuit board 82.
When the case 60 is mounted on the circuit board 82, the connecting spring plate 62 is bent and the end of the plate is contacted with a terminal of the circuit board 82.
Therefore, if there is formed a gap between the case 60 and the circuit board 82, the contact of the spring plate 62 with the terminal is kept.
FIG. 10 is a sectional view showing a further conventional connecting terminal device. A lead plate 71 is embedded in a speaker body 70. A cord 72 is fixed to the lead plate 71 by solder 74. A plug 73 is connected to the cord 72 and connected to a socket 75 on the circuit board 82.
However, when each of the above described conventional sound generators falls and collides with a hard ground, the coil spring 59 or spring plate 62 disengages from the terminal. Furthermore, there must be provided a plurality of jigs for accurately soldering the coil spring or spring plate, which requires multiple manufacturing steps. In the case using the cord, it is necessary to provide expensive plug and socket.
An object of the present invention is to provide a speaker having an external connecting terminal structure which has a high reliability and may be simply manufactured without accuracy jigs, and at a low cost.
According to the present invention, there is provided a speaker having a frame provided with a yoke, a magnet, a vibrating plate and a voice coil, and a pair of leads, wherein an end of each of the leads is connected to an end of the voice coil and the other end portion of the lead is secured to the frame and the underside of the other end portion is exposed, a terminal connecting device is provided for connecting the lead to an outside terminal, the terminal connecting device comprises a cylindrical case secured to the frame, a connecting rod slidably mounted in the cylindrical case, a coil spring provided in the cylindrical case to outwardly urge the connecting rod so as to be contacted with the outside terminal at an end of the connecting rod, and means for contacting the cylindrical case with the other end portion of the lead.
In an aspect of the invention, the means is engagement of a projection of the cylindrical case with a hole formed in the other end of the lead so as to keep the contact of the cylindrical case with the end of the lead.
In another aspect of the invention, the means comprises a ball provided in the cylindrical case so as to be outwardly urged by the coil spring to be contacted with an inside wall of a hole formed in the end of the lead.
The end of the connecting rod has a spherical shape.
The cylindrical case is secured in a hole formed in the frame in force fit engagement.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.